The present invention relates to the field of body fluid analyses in order to make a diagnosis or to monitor the concentration of analytes such as the blood glucose concentration.
The invention concerns a device or system for sampling small amounts of body fluid. A body fluid sampling device may comprise a skin piercing element with a fluid pathway for receiving body fluid therein. At least a portion of the fluid pathway is open to the environment. The sampling device further comprises a fluid receiving means which is separated from the fluid pathway so that fluid in the pathway will not contact the fluid receiving means in a first (separated) state. The device or system can be brought into a second state in which at least a portion of the pathway contacts the fluid receiving means so that fluid is transferred. Based on signals from a sensor of the fluid receiving means analyte concentration can be determined.
Systems for sampling body fluids are already known in the prior art in which body fluid is taken up into a disposable element. Blood collection and analytical systems are e.g. known from the document EP 0 199 484 which comprise a disposable unit with a capillary to collect body fluid and to transport the body fluid into a detection area. The further development of this concept is described in WO 97/42888. The arrangement described in this patent is particularly suitable for collecting relatively small amounts of body fluids which is primarily accomplished by pressing a ring onto the area surrounding a collection site and a pump movement. A system for analysis based on small amounts of interstitial fluid is known from EP 0 723 418. For this purpose a very thin closed hollow needle is inserted into the dermis and interstitial fluid is conveyed through the needle to a test zone by applying pressure to the area surrounding the puncture site. A highly miniaturized arrangement which also utilizes a closed needle to withdraw body fluid is known from U.S. Pat. No. 5,801,057. A particular advantage of this arrangement is the extremely thin needle which can be inserted into the arm region of a patient without essentially any pain.
Whereas the arrangement described in U.S. Pat. No. 5,801,057 already fulfils numerous practical requirements, some features are in need of improvement. A general problem with the sampling devices according to the previously mentioned document is to manufacture the hollow needle cost-effectively and as small as possible.
With this aim body fluid samplers which have an open fluid pathway structure are contemplated. The documents US 2003/0018282 and US 2003/0028125 both describe skin piercing devices which have an open channel for body fluid sampling which at least partially is located in a region of a piercing needle. Body fluid sampled into the fluid pathway is transferred to a testing zone which is fixed to the skin piercing element. In particular US 2003/0028125 describes that the skin piercing element is integral with a part of a test strip. A further document that contemplates a similar sampling and testing device with provision of a pooling area is described in US 2002/0168290.